As a private company, but one with arguably an unprecedented influence and commercial impact, Facebook's revenues have always been closely followed. On its scale, it epitomises the challenge of next generation social sites who now need to prove that there is real money behind the social media phenomenon. The latest reported figures look extremely good.

Ahead of an expected IPO early next year, it's more than a little convenient that some very healthy revenue numbers have "leaked" to Reuters. Scepticism aside, how do they look?

According to one source, Reuters reports, revenues reached $1.6bn for the first half of 2011, with net income at $500m. There's no breakdown of how much of that is made up of advertising and how much comes from revenue sharing on virtual goods in games and apps.

In the documents Goldman Sachs used to hawk its secondary market investment deal to potential investors, the firm claimed Facebook's revenues totalled $1.2bn for the first three quarters of 2010, with net income of $355m. That was roughly in line with some rather woolly media reports that ranged from $1.2bn to $2bn for the full year. That means Facebook's revenues have roughly doubled year on year.

Its implied valuation, meanwhile, on the slightly inflated secondary markets, has reached $80bn. VentureBeat says the latest figures show something like a 30% profit margin. Given that profit is an important factor in working out a company's value for an IPO, this looks very healthy. Public companies Microsoft and Google have profit margins over 30% while newly-public LinkedIn is at just 4.43%.

But VentureBeat also suggests the convenient timing of these figures, quoting the chief of research firm PrivCo who points to Facebook's vulnerability of users. "Facebook's revenue is heavily tied to participation. Once that drops, its revenue is going to decline," said Sam Hamadeh, pointing to falling growth in unique user figures in peak markets including the US and UK in May last year.

PrivCo puts Facebook's revenue from virtual goods at $670m for 2011, and advertising at $2.475bn for the year. Total revenues for 2011 it estimates at $3.145bn.

While Facebook will be happy for growing revenues to be leaked to firm up its financial credibility ahead of its IPO, it has already made moves to address the issue of saturating user numbers. Founder Mark Zuckerberg sketched out this "strategy" during the Skype partnership announcement; that unique user numbers are no longer the default traffic measurement, he decreed. Instead, it's about the volume of sharing which, he said, is a better representation of activity. Conveniently.